Sorry I'm quite new to Yii so don't know exactly how it all hangs. I was hoping it was just a matter of dumping all Yii generated files in my hosting account and off I go but I guess its more that that

I am on a paid hosting plan with 100webspace.com. They have php installed and I have ftp access to my site.
However they said Yii is not supported.
Is having ftp enough to get Yii going? Or does it require more from your host?
Do they have to install Yii on their hosting server or something?

I won't recommend free or shared server for a Yii based app, unless it is your personal project. A better alternative is an infrastructure, like DO or vultr. If you don't know how to set it up, you can use platform, like Cloudways (https://www.cloudway...yii-hosting.php )for automating server setup process. Using this platform you don't have to manually install OS or stack. Just select server size and datacenter location. Once server is ready, which will take few minutes, ssh to the server and install yii through composer command. Next deploy app from github or sftp. Composer and github comes pre-installed.